First report of leaf rust of blueberry caused by Thekopsora minima in Mexico.
Blueberry (Vaccinium corymbosum) is becoming an important crop in the states of Jalisco and Michoacan in Mexico. Leaf rust, a disease causing extensive defoliation on plants with severe infections, was observed in the autumn of 2007 and it has become one of the most significant diseases of blueberry in these states. Symptoms on the upper surfaces of leaves appear as small, yellow spots that later turn necrotic as they enlarge and coalesce and eventually cover large areas of individual leaves. On the undersides of leaves, small flecks sorrounded by small water-soaked halos appear, turn yellow, and produce powdery sori that are uredinia with urediniospores. On the basis of uredinial morphology, sequence data of ITS region of rDNA and pathogenicity tests, the rust was identified as Thekopsora minima. This is thought to be the first report of T. minima in Mexico. This report is significant for growers who need a diagnosis to control the disease and for breeders and plant pathologists who should consider developing more resistant cultivars.